Passenger railroad cars are supported on wheeled trucks located beneath opposite ends of each car. Each truck includes at least two pairs of wheels with each wheel pair being respectively interconnected with an axle at opposite ends thereof. A separate disc brake assembly and a separate tread brake assembly is mounted to the truck adjacent each wheel in a well known manner to impart a braking force to slow or stop the train.
Both the disc and tread brakes utilize brake actuator units which are air actuated to extend piston and cylinder controlled disc and tread brake components into braking contact with the axle and wheels, respectively. The brake units also each include a slack adjuster mechanism that automatically adjusts the position of the brake components to account for wear during use.
The aforesaid brake assemblies are pressure tested frequently (e.g. daily) to ensure operability. If an assembly fails, it is immediately replaced and returned to a backshop overhaul environment for overhaul and retesting. In addition, at less frequent intervals (e.g. every 3-4 years) as mandated by appropriate association or government control (e.g. The Association of American Railroads and the Federal Railroad Administration), the passenger coach cars are overhauled in the backshop environment, where all of the car components are replaced with new or reconditioned components.
During the overhaul process, in the past, the overhauled (or new) tread brake and disc brake actuator units were subjected to testing for pneumatic leakage in accordance with manufacturer supplied guide lines before being mounted back on to the truck. Conventionally, this testing has occurred by bolting the brake actuator unit to a test stand and then applying pressurized air to extend the actuator piston. A pressure gauge was used to check manually for pneumatic leakage as determined by visual inspection of the gauge needle by the test operator for pressure drop within a certain amount of time.
Since tread and disc brakes with their associated brake actuator units are manufactured by a variety of different manufacturers, the vertical support section of the test stand must be tailored to attach to the particular shape of the actuator cylinder casing. Since each manufacturers' brake actuator unit is different from other manufacturers' units, the same test stand cannot be used to test the other manufacturers' units. Differently configured test stands are respectively required to test the actuator units of the different manufacturers.
The aforesaid test protocol for testing for pneumatic leakage is fraught with human subjectivity and error since the test operator is required to observe small needle pressure drops (e.g. half pound or less) over a relatively long period of time. (e.g. two minutes). Since the small pressure drop manifests itself as a slight needle fluctuation on the pressure gauge, the possibility of human error in failure to detect a slight fluctuation is high.
Additionally, the inability to test a plurality of brake actuator units simultaneously unnecessarily prolongs and considerably slows down the overhaul process of the railway cars, particularly in a backshop overhaul environment.
It is accordingly an object of the present invention to simultaneously check a plurality of brake actuator units in a reliable, rapid and repeatable manner.
Another object is to test brake actuator units made by different manufacturers on the same test stand.
Still a further object is to eliminate human subjectivity and error in determining whether a brake actuator unit under test experiences air leakage.
Yet another object is to provide a test stand that performs a multitude of tests.
A further object is to provide a test stand for performing one or more tests on disc brake actuator units during an overhaul or replacement process.